docs: def init(banner, hidden, backup):
      """Initialize a manage shell in current directory
          $ manage init --banner="My awesome app shell"
          initializing manage...
          creating manage.yml
      """
      manage_file = HIDDEN_MANAGE_FILE if hidden else MANAGE_FILE
      if os.path.exists(manage_file):
          if not click.confirm('Rewrite {0}?'.format(manage_file)):
              return
  
          if backup:
              bck = '.bck_{0}'.format(manage_file)
              with open(manage_file, 'r') as source, open(bck, 'w') as bck_file:
                  bck_file.write(source.read())
  
      with open(manage_file, 'w') as output:
          data = default_manage_dict
          if banner:
              data['shell']['banner']['message'] = banner
          output.write(yaml.dump(data, default_flow_style=False))